. The eggs of mammals. Ovum; Embryology -- Mammals; Mammals -- physiology; Ovum. 86 THE EGGS OF MAMMALS for some 4 (in fertile matings) to 7 (in infertile matings) hours, during which time the ascending sperms are collect- ing in its lower layers (see Figure 28). The accumulation of sperms so effected ensures that sufficient shall be available to fertilise the ova as they emerge from the plug. As the sperms are put in progressively later than normal in relation to the time of ovulation, the accumulation of sperms be- comes progressively less and the chances of all the ova FALLOPIAN TUBE. PLUG
. The eggs of mammals. Ovum; Embryology -- Mammals; Mammals -- physiology; Ovum. 86 THE EGGS OF MAMMALS for some 4 (in fertile matings) to 7 (in infertile matings) hours, during which time the ascending sperms are collect- ing in its lower layers (see Figure 28). The accumulation of sperms so effected ensures that sufficient shall be available to fertilise the ova as they emerge from the plug. As the sperms are put in progressively later than normal in relation to the time of ovulation, the accumulation of sperms be- comes progressively less and the chances of all the ova FALLOPIAN TUBE. PLUG CONTAINING OVA Fig. 28. Diagram illustrating how the chances of the ova becoming fertilized are reduced as the interval between mating and ovulation is reduced, a = amount of sperm swarm which would accumulate if mating were made at the ordinary time—10 hours before ovulation, b = amount of sperm swarm which would accumulate if mating were made 4 hours before ovulation. (From the Journal of Ex-perimental Biology.) becoming fertilised are reduced in proportion to the time the fertile mating is delayed with reference to the time of o\ailation. ^^The ascent of the sperms can be represented as a curve (see Figure 28 and Hammond and Asdell, 1926) or as a swarm (in the statistical sense). The apex of the sperm swarm (shown, in order to assist visualisation of the prob- lem, very diagrammatically in Figure 28) reaches the top of the tube just at the time the plug is formed, , at ovu- lation, and so during the time that the plug exists (about 4 hours) it dams up but few sperms as compared with a normal mating made 10 hours before ovulation when the sperm swarm has ascended further (to the point a in Fig- ure 28).'^. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Pincus, Gregory, 1903-1967. New York, The Macmi
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